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Old 07-22-2015, 07:49 PM   #1
zjmarlow
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Missing some of 4GB RAM with 64-bit processor but 32-bit PAE motherboard chipset


Only seeing about 3GB of 4GB RAM on a machine with 64-bit processor but 32-bit PAE motherboard (http://ark.intel.com/products/27733/...ory-Controller).

Is there an install that would allow me to use all my RAM (e.g. installing the 32-bit version of Debian with PAE kernel - almost posted this in newbie section; correct me if I'm way off)?
 
Old 07-22-2015, 08:40 PM   #2
Timothy Miller
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So you're saying you have the 32-bit distro installed, with a PAE kernel? Sorry if it sounds stupid, but your wording makes it difficult to tell if that's what you're saying or not.

Last edited by Timothy Miller; 07-22-2015 at 08:42 PM.
 
Old 07-22-2015, 08:45 PM   #3
zjmarlow
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Sorry. I was asking if such an install would allow me to use all 4GB. I currently have the 64-bit distribution installed.
 
Old 07-22-2015, 08:50 PM   #4
Timothy Miller
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64-bit should definitely see all the ram, although yes, 32-bit PAE should also. Can you post the output of /proc/meminfo as your machine is currently running?
 
Old 07-22-2015, 09:05 PM   #5
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On a system with 4GB of physical RAM your mainboard has to fulfill these requirements for a 64 bit OS to use all of the physical RAM:
- No/Disabled integrated video controller
- BIOS must support (and have enabled) memory remapping

If one or more of these reuirements is not fulfilled your OS can and will not be able to use all the RAM.
 
Old 07-22-2015, 09:53 PM   #6
Timothy Miller
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I'm betting it's the onboard graphics, as the 915G did have onboard graphics (really poor 3d performance too, I had a desktop with one for a bit).
 
Old 07-22-2015, 10:10 PM   #7
zjmarlow
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Remapping of PCIE/APIC isn't listed as not supported on Wikipedia: https://en.wikipedia.org/wiki/List_of_Intel_chipsets.
Yes it has on board graphics.

Would I gain anything by switching to the 32-bit install with PAE kernel (understanding that I will still be losing some RAM to the integrated video controller)?
 
Old 07-22-2015, 11:01 PM   #8
Timothy Miller
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Nowadays, nothing I can think of. If supported by the hardware (which obviously yours is since you installed it), 64-bit will almost always perform AT LEAST identical to, if not better than, 32-bit OS.

I'd still like to see the meminfo though, just to know how much ram it actually does see, since that onboard graphics should only consume I think at max 256 MB.
 
Old 07-23-2015, 03:27 AM   #9
zjmarlow
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Thank you two for your replies.

TM, please let me know if you want the entire output; here's the total:

Code:
$ cat /proc/meminfo
MemTotal:        3082876 kB
...
 
Old 07-23-2015, 04:01 AM   #10
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Quote:
Originally Posted by zjmarlow View Post
Remapping of PCIE/APIC isn't listed as not supported on Wikipedia: https://en.wikipedia.org/wiki/List_of_Intel_chipsets.
Being supported by the chipset is not enough. It has to be supported by the BIOS/UEFI and enabled in them.
Quote:

Would I gain anything by switching to the 32-bit install with PAE kernel (understanding that I will still be losing some RAM to the integrated video controller)?
No.
 
Old 07-23-2015, 07:45 AM   #11
Timothy Miller
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Quote:
Originally Posted by zjmarlow View Post
Thank you two for your replies.

TM, please let me know if you want the entire output; here's the total:

Code:
$ cat /proc/meminfo
MemTotal:        3082876 kB
...
Yeah, that's kinda weird, it's seeing just 3 GB. Either it's sharing a lot more than I remember it being able to, or something is off.
 
Old 07-25-2015, 08:51 AM   #12
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On board graphics shouldn't be using that much RAM. You might try ram chip roullete. Shuffle the things around and see if it's not a hardware issue. Also make sure the bios is set to the lowest common denominator, not all ram chips support the same memory speeds. Although using the fastest RAM for your system makes a noticeable bump for intergrated graphics with shared ram. You might be able to set the shared RAM amount for the GPU in the bios. But it still seems a bit like a hardware issue to me.

$ free

$ cat /proc/meminfo
 
Old 07-26-2015, 11:41 AM   #13
zjmarlow
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Thanks guys for the replies.

Quote:
Originally Posted by Shadow_7 View Post
... Also make sure the bios is set to the lowest common denominator, not all ram chips support the same memory speeds...
All the modules are identical and basically brand-new. I'll give shuffling things around a bit a try anyway and post back.
 
  


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